The present disclosure relates to an illumination device and a display device, each device having a light modulator that may scatter or transmit light, and a method of manufacturing the light modulator.
Recently, a liquid crystal display is remarkably improved in image quality or remarkably advanced in power saving, and a method is proposed to improve scotopic contrast, where the contrast is improved by partially modulating intensity of light from a backlight. The method is largely designed to partially drive light emitting diodes (LED) as a light source of a backlight so that light from the backlight is modulated in accordance with a display image. Furthermore, thickness reduction is now increasingly demanded not only to a small liquid crystal display, but also to a large liquid crystal display. Therefore, an edge light type of backlight, where a light source is disposed at an end of a light guide plate, is noted instead of a backlight type where a cold cathode fluorescent lamp (CCFL) or LED is disposed directly below a liquid crystal panel. However, the edge light type is hard to enable partial drive of partially modulating light intensity of a light source.
For example, Japanese Unexamined Patent Application, Publication No. 6-347790 proposes a display device using a polymer dispersed liquid crystal (PDLC), which is changed between a transparent state and a scatterable state, as a technique of extracting light being propagated through the light guide plate. This is a technique for preventing mirroring, where voltage is partially applied to the PDLC so that the PDLC is partially changed between the transparent state and the scatterable state.
In the edge light backlight, for example, a technique is known, in which a printing pattern, coarseness of a light extraction pattern, or size of a pattern is changed depending on a distance from a light source such as LED or CCFL (for example, refer to Japanese Unexamined Patent Application, Publication No. 11-142843). The technique described in the Patent Application is a kind of technique for uniformly extracting light from a light guide plate, and designed only in consideration of light extraction. In addition, for example, a technique is known as a technique for making luminance uniform in a plane, in which light diffusivity of a diffuser sheet is gradually changed in accordance with a distance from a light source (for example, refer to Japanese Unexamined Patent Application, Publication No. 2004-253335).
For example, it is considered that the technique of the Patent Application, Publication No. 11-142843 or 2004-253335 is combined with the PDLC of the Patent Application, Publication No. 6-347790 so that luminance of light from the backlight is made uniform in a plane. However, in such a case, while luminance may be made uniform, luminance in dark display is increased, resulting in a difficulty that a modulation ratio between bright display luminance and dark display luminance may not be increased.
It is desirable to provide an illumination device and a display device, in which a modulation ratio may be increased while luminance is made uniform in a plane, and a method of manufacturing a light modulator.